Manufacture of nitric acid esters



May 27, 1941. J. F. OLIN MANUFACTURE OF NITRIC ACID ESTER S Filed Nov.l5, 1938 Q kw? QE O .xkmeow I INVENIOR: JOHNF.OL1N W QM A TTORNE YPatented May 27, 1941 MANJJFACTURE F NITRIC ACID ESTERS John F. Olin,Grosse Ile, Mich assi'g nor to 'lhe Sharples Solvents Corporation;Philadelphia, Pa.

Application November 15, 1938;,Se1'ia1-No.'240,513

Claims.

pered by the lack of a process for producing suchmaterials on acommercial scale at a reasonable price. Under prior art practice theyields of nitrated products, with very few exceptions, are low and theoperations are dangerous.

Two procedures for the preparation of nitrates frommethyl, ethyl,propyl, butyl and amyl alcohols have been described. One method, whichhas been used to prepare nitrates from monohydric. alcohols containingnot more than three carbon atoms, consists essentially in thedistillation of a mixture of nitric acid and alcohol in thepresence ofurea. readily; volatilized and may be distilled from the. reactionzoneto prevent accumulation of the ester the: nitrating vessel which mightotherwise result'in explosions.- Since the presence of even smallamounts of nitrous'acid tends.

to initiate a vigorous auto-oxidation of explosive violence, urea isadded to decompose nitrous acid as formed. in accordance with the.following equation:

CCKNHZ)2+2HNO2=CO2+2N2+3H2O By the above process the methyl and ethylnitrates maybe prepared with fairly good results, but the method is notsuitable for the nitration of alcohols containing four or more carbonatoms. In the case of the nitration of propyl or butyl alcohol oralcohols of higher carbon content than butyl alcohol, highertemperatures are required to obtain the esterification reaction thanwhen the lower alcohols are nitrated. Higher temperatures are alsorequired for distillation of theiesters from the nitration mixture inthe case of? higher alcohols than in the caseof the lower alcohols. Asthe result of these two facts,.

attemptsto nitrate propyl and higher alcohols have resulted in theoxidation of the alcohol to produce the corresponding aldehydathisoxidation reaction occurring incident to nitration of thealcoholandtherefore preventing the success.-

The nitration of aliphatic alcohols to.

The nitrate formed is.

ful practice of. the nitration process. In such cases the. oxidation ofthe alcohol can be to some. extent prevented'by the addition of urea totheireaction mixturabuteven when this precaution is taken the yield ofthe desired nitrate is still very low. In the coursezof the oxidationreaction occurring when attempts are made to nitrate the higheralcohols, the nitric acid intended for esterification" is. reduced tonitrous acid. Theoxidation of the alcohol is therefore a deleteriousreaction both from the standpoint of producing undesired b-y-productsand from the standpoint of reducing the esterifying acid. Evenwiththelowest alcohols the-yield is rarely in excess :of 75%(SystematicOrganic Chemistry, Cumming, Hop-per and Wheeler, page 254) Aprocess. of nitrating isoamyl alcohol which has beensuccessf-ul from alaboratory viewpoint involves the addition of isoamyl alcohol or amixture of the alcohol with concentrated sulfuric acid to anices-coldbathof nitric and concentrated sulfuric acid inthe volume ratio of 1:3.This processhas not achieved commercial success because of thediificulties of recovering unused nitric. acid and of reconcentratingthe sulfuric acid; A. more. serious defect of this method lies in: thefrequentexplosions occurring unless the alcohol is verypure.

Neither of the-above processes givessatisfactory resultsinthe nitrationof monohydrio alcoholsother than-primary alcohols and no satisfactorymethodhas-been heretofore-devised for the preparation of secondary alkylnitrates. The yields. obtained by treating asecondary ortertiaryaliphatic alcohol by. either of the methods ment-.with.35% to60% nitric acid. Concentrations. belowgave very low-grade esters whilethe -useof acid having a-nitric acid content in excess of resulted insubstantialoxidation with consequent-decreasein yield. The presentinventionrests upona procedure by which the objectionable-featuresofprior art processes are avoided bypassing the reactants to the reactionchamber in a continuousmanner and continuously passing; the reactionmixture from the reaction chamber, thismixture-being separated objecthas been to afford a satisfactory method of producing nitrates of propyland higher alcohols. The practice of the features of the invention isparticularly useful in producing alkyl nitrates by esterifying alcoholscontaining from 3' to 8 carbon atoms, inclusive, with nitric acid.

It may be logically inferred. that the esterification of an aliphaticalcohol proceeds through the formation of an oxonium derivative of verylow vapor pressure. From that intermediate compound, the ester is formedby loss of water, but in the presence of concentratednitric acid, theoxonium derivative is oxidized to. form undesired by-products. Thesereactions may be represented as follows:

1. CHHOH+HONO2=C5H11OH.HONO2 Amyl alcohol Nitric Oxonium derivative 2.C5H OH.HONOz=C5H ONO2+H2O Oxonium derivative Amyl nitrate W ater 3.C5HnOH.HONO2=C4HaCHOI-HNO2 Oxonium derivative Valeralde- Nitrous hydeacid In the above equations the reactions represented by Equations 1 and2 are the desirable reactions, while the reaction represented byEquation 3 is the undesirable reaction, since it results in theformation of undesired valeraldehyde and reduction of the nitric acidwhich might otherwise be converted into amyl nitrate.

When concentrated nitric acid is used in the practice of the process ofnitration as indicated by Equations 1 to 3 above, the reactions ofEquations 1 and 3 predominate; and the desired reaction of Equation 2 isdepressed.

When concentrated nitric acid is used, the concentrated nitric acid alsocauses auto-oxidation of the alkyl nitrate formed in accordance withEquation 2 above, with the result that thecontents of the reactionvessel frequently explode.

On the other hand, when very dilute nitric acid is employed in thisreaction, the reaction is extremely slow and the yields of the desiredproducts are small.

The operator, desiring to produce amyl nitrate, for example, is on thehorns of a dilemmawhen attempting to operate in accordance with theprior art procedure for producing methyl and ethyl nitrates. If heinitiates the reaction with the use of a concentrated nitric acid, theinitial reaction involves undesired production of valeraldehyde andreduction of the nitric acid as indicated in Equation 3. If, on theother hand, he initiates the reaction by the use of nitric acid of theconcentration found most suitable for the accomplishment of thereactions of Equations 1 and 2, water formed incident to theesterification reaction as indicated in Equation 2 rapidly dilutes thereaction mixture and reduces the nitric acid to a concentration at whichitwill not eificiently perform its nitrating function.

Reasoning from the above premises, the apauto-oxidation of the alkylnitrate formed in accordance with Equation 2.

reaction vessel I3 at this time.

In accordance with the present invention, autooxidation in theesterification vessel is prevented by removing the alkyl nitrate fromthe esterification vessel promptly after the formation thereof. This isaccomplished by passing the reactants continuously through the reactionapparatus, nitric acid, the alcohol to be esterified and an amount ofurea sufficient to inhibit auto-oxidation bein continuously passed tothe reaction vessel and a mixture of alkyl nitrate, alcohol, nitric acidand water being continuously discharged from the 'esterification vessel.By proceeding in this manner, the concentration of nitric acid in theesterification vessel may be maintained substantially constant, sincethe water of esterification is removed from that vessel at the same rateat which it is formed incident to the esterification. The reactionmixture is thereafter separated into its constituents by extraction anddistillation steps to be described hereinafter.

Since there is usually a tendency toward formation of nitrous acid inthe reaction mass which will initiate oxidation if permitted toaccumulate, it is preferred that a small proportion of urea be added tothe vessel in which the present process is practiced. As a general rulethe proportion of urea added is less than that employed in the processof the prior art, but as a precaution agains decreased yields, inferiorgrade ester, and explosion it is always well to follow the practice ofadding at least a small amount of urea.

In its preferred embodiment the invention may be advantageouslypracticed in the apparatus shown diagrammatically in the accompanyingdrawing wherein I0, H and I2 designate storage tanks which may containnitric acid of the desired concentration, an alcohol and 50% ureasolution respectively, and each of these tanks is connected by a valvedpipe to reaction vessel I3, which is provided with an agitator and aheating coil.

In the practice of the invention, nitric acid is first passed into thereaction vessel I3 to a level slightly below the level of the takeoffline which connects that vessel with the mixer I4. A small quantity ofurea is also preferably passed to the The nitric acid is then heated tothe desired temperature at which it is reacted with the alcohol to beesterifled. Quantities of alcohol from tank II and an excess of nitricacid from tank III are then run continuously into the esterificationvessel I3. Since the temperature in the reaction vessel I3 is at thepoint best facilitating the reaction, the alcohol and nitric acid willreact promptly upon contact with each other in that vessel. The reactionmixture, containing the desired alkyl nitrate, unreacted nitric acid,water of esterification, urea and alcohol, passes continuouslyfrom theesterification vessel I3 to a mixer I4, which is provided with amechanical agitator.

The rate of withdrawal of the reaction mixture fromthe esteriflcationvessel I3 tothe mixer.

I4 is substantially the same as the rate of passage of nitric acid andalcohol from containers l and H to the esterification vessel. A solventfor the ester content of the reaction mixture is continuously passedfrom tank l5 to mixer It in such proportion as to selectively dissolvethe ester and alcohol in the mixer hi to the substantial exclusion ofnitric acid and water. The solvent added in mixer I l may be any good,inert, oil solvent, such as benzene, toluene, hexane, heptane, ether ora chlorinated hydrocarbon solvent such as carbon tetrachloride. In casethe ester formed is heavier than the nitric acid solution contained inthe mixture passed to the mixer M, it is preferable to employ a solventof highspecific gravity, such as carbon tetra chloride, in order tofacilitate subsequent separation of the solution of ester and alcohol inthe solvent from the nitric acid of the reaction mixture. In cases inwhich, on the other hand, the ester formed is lighter than the nitricacid solution passed to the mixer l4, it is preferred to employ a.solvent of lower specific gravity than that of the nitric acid solution,such as benzene, toluene, hexane, heptane or ether. i5 is preferablyprovided with a coil, through which a cooling liquid is circulated inorder to prevent volatilization in case a high volatile solvent, such asother, is employed.

The mixture of nitric acid solution and solution of ester and alcohol inthe solvent is next passed to a decanter IS, in which the major part ofthe nitric acid solution is removed from the solution of ester andalcohol in the solvent from tank I 5. The nitric acid solution may bepassed to receiver IT for subsequent fractionation to remove organicconstituents and reconcentration. The solution of ester and alcohol inthe solvent is passed from decanter It to a mixer 18. It is to be notedat this point that, if thenitric acid solution is of lower specificgravity than the ester solution (oil layer) decanted from decanter IS,the decanter connections will be reversed, the lighter efiluent (nitricacid solution) being passed to receiver ll and the heavier effluent toreceiver I53.

Water from tank 59 is mixed with the oil layer passing to tank 38 fromdecanter l6, and the mixture so produced is passed continuously to adecanter is, where the aqueous layer is removed and sent to the receiver:7. The oil layer from decanter 99 (which may be the lighter or heavierlayer, depending upon the specific gravity of the ester produced and thespecific gravity of the solvent used) is passed continuously to a mixer28, where it is treated with an aqueous alkaline solution, such as asodium carbonate solution, which removes the last traces of free acid.This alkaline solution is passed from tank 22 to the mixer 2d and themixture produced in the mixer 28 is then passed to a decanter 2 l, whicheffects removal from the oily solution of the alkaline aqueous liquidproduced in mixer 2d. The aqueous alkaline solution is passed toreceiver 23 the oil layer from decanter 2i is passed to a mixer where itis again mixed with water from container is The mixture from mixer 24 ispassed to a decanter 25, from which the aqueone layer is passed toreceiver 23, while the oil layer is passed to stripping apparatus to bedescribed hereinafter.

The material collected in the receiver 23, like the material collectedin receiver H, is subjected to a stripping operation to remove unusedalcohol, and this unused alcohol may be returned The mixer small.

to the tank II. The oil layer from decanter 25 is next passed to astripping column 26, which is maintained at such a temperature that thesolvent passes overhead and is condensed in condenser 21 and returned tothe tank i5. A residue consisting of unused alcohol and the nitric acidester collects in the still 28, and this residue is pumped into column28, which is operated at such a temperature as to pass the alcoholoverhead in the form of a binary constant boiling mixture containing apart of the alkyl nitrate. This overhead fraction is condensed incondenser 39. A part of the condensate is refluxed to column 29 andanother part may be returned to tank I l as illustrated.

After separation of the alcohol content of this mixture from the desirednitrate, this alcohol may be returned to storage tank I l. Alkyl nitrateis pumped from the still 3i into a column 32, where further purificationof this ester is obtained, followed by condensation in the condenser3:3. The ester so obtained from condenser 34 is sufficiently pure to beused commercially. In cases in which relatively high boiling esters areproduced, it is preferable to maintain the columns 26, 2e and 32 undersub-atmospheric pressure in order to avoid decomposition of theseesters, which might occur in case the temperatures necessary to effectdistillation at atmospheric pressure were employed.

The use of concentrated acid, that is, nitric acid containingsubstantially more than 70% HNOa, is possible under very closelycontrolled conditions, but should be avoided in most nitration reactionsof the present type. The term dilute nitric acid as used in thisdisclosure and in the claims appended hereto is to be understood asreferring to an acid containing HNOs not substantially in excess of 70%.It has been noted that extremely dilute acids generally give slowreactions and poor conversions and although some of the benefits of thisinvention may be obtained with acid of low concentration it is usual lyfound that better results are obtained when using nitric acid having anHNG3 content in excess of i. e., in which the total water content of theesterification vessel does not bear a ratio to the total I-INO3 contentof greater than 70:30. While acids having a concentration between about30% and 65% give highly satisfactory results as compared with priorprocesses, the preferred range is to concentration of nitric acid sincea reagent within the latter limits has been found generally suitable tothe nitration of alcoholsesterified in accordance with the presentinvention. The acid added continuously to the esterification vesselshould be of somewhat higher concentration than the concentration ofacid which it is desired to maintain in that vessel, since acidcontinuously added to the vessel will be diluted to the desired concentration by the water of esterification formed in that vessel. Afairly good general rule is that lower acid concentrations should beused in connection with alcohols having a greater number of substituentson the carbinol group, e. that lower acid concentrations should be usedin esteriiying secondary alcohols than primary alcohols.

The use of urea is recommended to oxidation. The process here describedrepresents a striking improvement over the prior art by depressing sidereactions to the very minimum and the amount of urearequired istherefore very The low cost of this reagent in the amounts used in thepreferred embodiment of this invention is fully justified by theadditional safety and improved yield obtained thereby. In connectionwith the nitration of primary alcohols, such as butanol-l, very littleof the oxidation inhibitor is normally used, while more liighlysubstituted carbinols generally require appreciable amounts of thisreagent.

Example 1--Preparation normal propyl nitrate.--Reaction vessel I3 ischarged with 60% nitric acid and a 50% solution of urea in water isadded from tank l2 in an amount constituting of the weight of nitricacid in the esterification vessel I3. Steam is then passed into theheating coil of the vessel 13 until the contents are raised to atemperature between 80 and 85 C. The agitator in the vessel i3 is thenstarted and further quantities of 70% nitric acid from tank I0 andnormal propyl alcohol from tank II are run in, in approm'mate Volumeratio of 1.3 to 1. As the reaction proceeds, further quantities of ureasolution in amounts necessary to inhibit oxidation are added.Simultaneously with the addition of acid, alcohol and urea liquidoverflows from esterification vessel l3 into mixer l4, and the mixturein mixer I4 is reduced to a temperature of 25 C. An amount of normalhexane equal in volume to the volume of alcohol passed from tank I I tovessel I3, is continuously supplied to the mixer Hi. The mixture passingfrom mixer I4 is decanted in decanter l6 and the oil layer from decanterI5 is further washed and decanted, as indicated in the abovedescription. The Washed ester from decanter 25 is then passed intocolumn 26, where the hexane containing traces of propyl alcohol andpropyl nitrate is passed overhead and returned to storage tank [5. Thebottoms from still 28 are then pumped into column 29, and the smallamount of propyl a1- cohol remaining in the crude mixture is passedoverhead, together with some propyl nitrate, and returned to storagetank II. The crude ester is then rectified by pumping it from still 3|into column 32 and obtaining relatively pure propyl nitrate boilingbetween 108 and 111 C. The ester produced in this manner has a specificgravity of 1.045.

In the case of the preparation of this ester, it is to be observed that,because of the solubility of propyl alcohol in the diluted nitric acidand in the aqueous wash water passed to receivers l1 and 23, only arelatively small quantity of propyl alcohol was recovered in thesubsequent distillation operations performed in columns 26 and 29.However, upon distillating the diluted acid from receiver l1 and thediluted alkaline washes from receiver 23, substantially all of thepropyl alcohol not accounted for as propyl rfitrate may be recovered.

Example Z-Jllixed amyl nitrates-In the manufacture of this material, 50%nitric acid is charged into vessel 13 to approximately a point one-thirdbelow the takeoff. Upon heating to 90 C., esterification is caused totake place by the continuous addition of amyl alcohol and 65% nitricacid; the latter being used in 50% excess, or such excess as is requiredto maintain the free acid at 40-50%. Benzene may be used as a solventinstead of hexane, if desired, and theabsolute .pressure inthefractionation columns 26, 29 and 32 is preferably reduced to 200 mm. Theprocess is otherwise identical with that described in Example 1. Themixed amyl nitrate material obtained by conducting the process in thismanner in the esterificatio-n with the mixture of amyl alcohol,commercially known as Pentasol, has a specific gravity at a temperatureof C. of 0.988, and boils between 142 and 154.2" C. This mixture is acolorless liquid and has a pleasant odor.

From the above discussion, the manner in which the objects of theinvention have been attained will be apparent. By conducting thereaction continuously, and removing the reaction mixture from theesterification vessel as formed, conditions in the esterification vesselare maintained substantially constant, and may be maintained at thepoint found most suitable for esterification of the particular alcoholbeing reacted with nitric acid. By operating in this manner, thedisadvantage inherent in operating in accordance With prior artprocedure of progressive dilution of the nitric acid is avoided. In Viewof this fact, it is not necessary to initiate the practice of theprocess by the use of acid of higher concentration than that mostsatisfactory for the preparation of the desired ester, and all of thedisadvantages of the prior art discussed above are thus obviated.

While specific apparatus has been described in the foregoing descriptionof the invention, 1 wish it understood that the invention is in no waylimited to such specific apparatus, but that, it may be practiced in anyapparatus suitable for the performance of the above-described processsteps. Thus, for example, the esterification vessel 13 does notnecessarily have to be a reaction vessel of the type illustrated, butmaybe any suitable column, coil, or other contacting device, in whichnitric acid of the desired strength is brought into contact withalcohol, and from which the reaction mixture is continuously dischargedto apparatus for the performance of a series of steps in which thereaction mixture is separated into its constituents, as described.

Still further modifications will be obvious to those skilled in the artand I do not therefore wish to be limited except by the scope of thesubjoined claims.

I claim:

1. The process of preparing an aliphatic nitrate which comprisescontinuously passing nitric acid of between forty-five and fifty-fivepercent concentration and an aliphatic alcohol together through areaction zone, continuously removing the reaction mixture from saidreaction zone during the feed of nitric acid and alcohol thereto, andthereafter separating the desired aliphatic nitrate from the reactionmixture so produced by solvent extraction.

2. The process of preparing an aliphatic nitrate which comprisescontinuously passing nitric acid and an aliphatic alcohol togetherthrough a reaction zone, continuously removing the reaction mixture fromsaid reaction zone during the feed of nitric acid and alcohol thereto,and thereafter separating the desired aliphatic nitrate from thereaction mixture so produced by a process in volving extraction of thereaction mixture with a solvent for said aliphatic nitrate.

3. The process of preparing an aliphatic nitrate which comprisescontinuously passing nitric acid and an aliphatic alcohol togetherthrough a reaction zone, continuously removing the reaction mixture fromsaid reaction zone during the feed of nitric acid and alcohol thereto,and thereafter separating the desired aliphatic nitrate from thereaction mixture so produced by a process involving extraction of thereaction mixture with a solvent chosen from the class consisting ofchlorinated hydrocarbons, benzene, toluene, hexane, heptane and {ether.

4. 'Thejprocess-of preparing an aliphatic nitrate-whieh comprisescontinuously'passing nitric acid and an aliphatic alcohol togetherthrough a reaction zone, continuously removing the reaction mixture fromsaid reaction zone during the feed of nitric acid and alcohol thereto,and thereafter separating the desired aliphatic nitrate from thereaction mixture so produced by a process involving extraction-ofthe'reactionmixture with a solvent for said aliphatic nitrate andsubsequent washing with water of the material dissolvedin the extractionsolvent.

5. The process of preparing an aliphatic'nitrate which comprisescontinuously passing nitric acid and an aliphatic alcohol togetherthrough a reaction zone, continuously removing the reaction ixture fromsaid reaction zone during the feed of nitric acid and alcohol thereto,and thereafter separating the desired aliphatic nitrate from. thereaction mixture so produced by a process involving extraction of thereaction mixture with a solvent for said aliphatic nitrate, washing withwater the material dissolved in the extraction solvent and subsequentlyneutralizing the waterwashe'dmix-ture by washing with abase.

6. The process of preparing an aliphaticnitrate which comprisescontinuously passing nitric acid and an aliphatic alcohol togetherthrough areaction zone, continuously removing the reaction mixture fromsaid reaction zone during the feed of nitricacid and alcohol thereto,and thereafter separating the desired aliphatic nitrate from. thereaction mixture so produced by a process involving extraction of thereaction mixture with a solvent for said aliphatic nitrate, washing withwater the material dissolved in the extraction solvent, neutralizing thewater-washed mixture by washing with a base and thereafter again washingthe solvent-extracted, water-washed and neutralized mixture with water.

7. The process of preparing an aliphatic nitrate which comprisescontinuously passing nitric acid and an aliphatic alcohol togetherthrough a reaction zone, continuousl removing the reaction mixture fromsaid reaction zone during the feed of nitric acid and alcohol thereto,and thereafter separating the desired aliphatic nitrate from thereaction mixture so produced by a process involving extraction of thereaction mixture with a solvent for said aliphatic nitrate andsubsequent distillation of the extracted organic constituents of thereaction mixture to separate solvent and alcohol therefrom.

8. The process of preparing an aliphatic nitrate which comprisescontinuously passing nitric acid and an aliphatic alcohol togetherthrough a reaction zone, continuously removing the reaction mixture fromsaid reaction zone during the feed of nitric acid and alcohol thereto,and thereafter separating the desired aliphatic nitrate from thereaction mixture so produced by a process involving extraction of thereaction mixture with a solvent for said aliphatic nitrate, washing withWater the material dissolved in the extraction solvent and subsequentdistillation of the extracted organic constituents of the reactionmixture to separate solvent and alcohol therefrom.

9. The process of preparing an aliphatic nitrate which comprisescontinuously passing nitric acid and an aliphatic alcohol togetherthrough a reaction zone, continuously removing the reaction mixture fromsaid reaction zone during the feed of nitric acid and alcohol thereto,and thereafter separating the desired aliphatic nitrate from thereaction mixture so produced by a process involving extraction of thereaction mixture with a solvent for said aliphatic nitrate, washing withwater the material dissolved in the extraction solvent, neutralizing thewater-washed mixture and subsequent distillation of the extractedorganic constituents of the reaction mixture to separatesolvent andalcohol therefrom.

10. The process of preparing an aliphatic nitrate which comprisescontinuously passing nitric acid and an aliphatic alcohol togetherthrough "a reaction zone, continuously removing the reaction mixturefrom said reaction zone during the feed of nitric acid and alcoholthereto, and thereafter separating the desired aliphaticnitrate fromthereaction mixture so producedbyva process involving extraction of thereaction mixture with a solvent for said aliphatic'nitrate andsubsequent distillation of the extracted organic constituents of thereaction mixture to separate solvent and alcohol therefrom and returningto the reaction zone alcoholrecovered in said distillation step.

11. The process of preparing an aliphatic nitrate which comprisescontinuously passing nitrio acid and an aliphatic alcohol togetherthrough a reaction zone,'continuously removing the reaction mixture fromsaid reaction zone during the feed of nitric acid and alcohol thereto,and thereafter separating the desired aliphatic nitrate from thereaction mixture so produced bya process involving extraction of thereaction mixture with a solvent for said aliphatic nitrate andsubsequent distillation of the extracted organic constituents of thereaction mixture to separate solvent and alcohol therefrom and returningto the solvent extraction step of the process solvent recovered in saiddistillation step.

12. The process of preparing an aliphatic nitrate which comprisescontinuously passing nitric acid and an aliphatic alcohol togetherthrough a reaction zone, continuously removing the reaction mixture fromsaid reaction zone at approximately the rate of feed 01' reactants tosaid reaction zone during the feed of nitric acid and alcohol thereto,and thereafter separating the desired aliphatic nitrate from thereaction mixture so produced by solvent extraction 13. The process ofpreparing an aliphatic nitrate which comprises continuously passingnitric acid and an aliphatic alcohol together through a reaction zone,continuously removing the reaction mixture from said reaction zoneduring the feed of nitric acid and alcohol thereto, and thereafterseparating the desired aliphatic nitrate from the reaction mixture soproduced by solvent extraction, the amount and concentration of acidcontinuously introduced into the reaction zone being so co-related tothe rate of Withdrawal of reactants from said zone as to maintain thedegree of concentration of aci in said zone substantially constant.

14. The process of preparing an aliphatic nitrate which comprisescontinuously passing nitric acid and an aliphatic alcohol containingbetween three and eight carbon atoms inclusive in its aliphatic radicaltogether through a reaction zone, continuously removing the reactionmixture from said reaction zone during the feed of nitric acid andalcohol thereto, and thereafter separating the desired aliphatic nitratefrom: the reaction mixture so produced by solvent extraction.

15. The process of preparing an aliphatic nitrate which comprisescontinuously passing nitric acid and an aliphatic alcohol containingbetween three and eight carbon atoms in its aliphatic radical togetherthrough a reaction zone, continuously removing the reaction mixture fromsaid reaction zone during the feed of nitric acid and alcohol thereto,and thereafter separating the desired aliphatic nitrate from thereaction mixture so produced by a process involving extraction of thereaction mixture with a solvent for said aliphatic nitrate, Washing withwater the material dissolved in the extraction solvent and subsequentdistillation of the extracted organic constituents of the reactionmixture to separate solvent and alcohol therefrom.

16. The process of preparing amyl nitrate, which comprises continuouslypassing nitric acid and amyl alcohol together through a reaction zone,continuously removing the reaction mixture from said reaction zoneduring the feed of nitric acid and amyl alcohol thereto, and thereafterseparating the desired amyl nitrate from the reaction mixture soproduced by solvent extraction.

17. The process of preparing amyl nitrate, which comprises continuouslypassing nitric acid and amyl alcohol together through a reaction zone,continuously removing the reaction mixture from said reaction zoneduring the feed of nitric acid and amyl alcohol thereto, and thereafterseparating the desired amyl nitrate from the reaction mixture soproduced by a process involving extraction of the reaction mixture withtrate which comprises continuously passing nitric acid and a monohydriealiphatic alcohol containing between three and eight carbon atomsinclusive in its aliphatic radical together through a reaction zone,continuously removing the reaction mixture from said reaction zoneduring the feed of nitric acid and alcohol thereto, and thereafterseparating the desired aliphatic nitrate from the reaction mixture soproduced by solvent extraction.

19. A process as defined in claim 18, in which the extraction of thealiphatic nitrate from the reaction mixture is accomplished by treatmentwith a solvent chosen from the class consisting of chlorinatedhydrocarbons, benzene, toluene, hexane, heptane and ether.

20. The process of extracting an aliphatic nitrate from a mixturecontaining said aliphatic nitrate, water, urea, nitric acid, and analiphatic alcohol which comprises extracting said reaction mixture witha solvent chosen from the class consisting of chlorinated hydrocarbons,benzene, toluene, hexane, heptane and ether,

JOHN F. OLIN.

